This invention relates to a compressor housing modification for the compressor portion of a turbocharger. The particular embodiment disclosed in this application relates to a compressor housing portion of a turbocharger such as is used on large diesel engines. However, the invention disclosed in this application can be applied to compressor housings used on other types of internal combustion engines. For purposes of illustration, the invention is described in this application in terms of a preexisting compressor housing manufactured with an integrally-formed throat. As described herein, the integrally-formed throat is removed and replaced with a separate throat insert which can be replaced and which can have different throat sizes for a given sized compressor housing.
A turbocharger increases the power available to an integral combustion engine by making use of the dynamic energy present in the rapidly moving exhaust gases which are removed from the compression chamber of the engine during each cycle. The exhaust gases are directed through a turbine and against a turbine wheel. The turbine wheel has blades which convert the energy in the exhaust gases into rotary motion of the wheel and the shaft on which the wheel rotates. On the other end of the same shaft is a compressor wheel mounted for rotation in a compressor housing. The rotation of the compressor wheel takes intake air being conveyed to the air intake manifold of the engine and compresses it. The energy added to the air during the compression process is released when the air is mixed with fuel and ignited, thereby increasing the available power output of the engine.
The shaft on which the turbine wheel and compressor wheel are mounted rotates at extremely high speeds. Accordingly, the shaft and wheels must be very delicately balanced and aligned relative to the turbine housing and compressor housing, respectively. For this reason, the shaft is very carefully mounted on bearings which not only control the rotation of the shaft but also the axial movement of the shaft between the compressor housing and the turbine housing. To achieve maximum efficiency, the shape of the turbine wheel and the compressor wheel must very closely correspond to the adjacent surfaces of the turbine housing and compressor housing, respectively. This is a particularly critical factor with regard to the compressor housing and the compressor wheel. In order to achieve a smooth, efficient and relatively quiet transfer of energy from the rapidly rotating compressor wheel to the air being fed to the engine, the cross-section of the compressor wheel and the corresponding cross-sectional surface of the compressor housing must be substantially the same. The compressor wheel is spaced-apart only so far as is necessary to prevent actual contact between the compressor wheel and the compressor housing. The portion of the compressor housing which corresponds to the cross-sectional shape of the compressor wheel is called the throat. The throat is an annular orifice which reduces in diameter as its surface moves away from the compressor wheel. In cross-section, its shape generally resembles that of a trumpet bell.
Occasionally, the bearings on which the compressor wheel shaft is mounted become loose and permit the compressor wheel to move into actual contact with the throat of the compressor housing. The rapid rotation of the compressor wheel quickly destroys the uniform shape of the throat. In some cases, the damage is relatively minor. In such instances, prior art repair of the compressor housing involves remachining the surface of the throat to restore to throat to its desired shape. However, if the damage to the throat involves deep scars or gashes, remachining it not possible because the remaining thickness of the throat would be below minimum specifications. Therefore, prior art methods of repairing compressor housings involve first a determination of the extent of damage to the compressor housing throat. If the damage is relatively minor, the throat surface is remachined as described above. If the damage is substantial, the compressor housing is scrapped even though the remainder of the compressor housing is completely satisfactory for continued use. Even when compressor housings can be remanufactured by remachining the throat, repaired compressor housings must be stocked in a wide variety of compressor housing types and throat diameters.
The necessity to maintain a large inventory of different sizes increases substantially the expense of repairing or overhauling engines since very often the repairs must be made on a emergency basis and there is no time to order correctly sized compressor housings from a centrally located parts depot. There has long existed a need for a way in which to use compressor housings, which have damaged throats but are otherwise in good condition and, also, a way to reduce substantially the number of compressor housings required to be carried in inventory in repair and overhaul facilities. The invention described in this application achieves both objectives in a novel manner.